Enabled discussions on Github

[Dawoodoz]

Github discussions are now enabled, so that anyone can show what they are doing with the library, share their engines, ask questions, answer others' questions, reply to polls, and make suggestions.

If you are a total beginner finding something difficult to use, the feedback about common missunderstandings will be even more valuable, by seeing how something that C++ programmers got used to can be simplified, leading to less bugs.